In the field of optical or optoelectronic modules, many such modules operate at two rates (e.g., so-called “dual-rate” modules). A laser in the transmitter portion of the module (a transmitter optical subassembly, or TOSA) may output data at each rate in a different mode of operation (e.g., a low-rate mode and a high-rate mode). The different modes may have a large operational or output power range from the high rate to the low rate, and the dynamic range of the current in a monitoring photodiode on a back facet of the transmitter laser is accordingly large.
A laser driver may drive the laser in the TOSA using the monitoring photodiode in closed-loop regulation, and the laser may have a target optical output power. However, the adjustable range of conventional laser drivers cannot cover all current distribution ranges of typical back facet monitoring photodiodes. Therefore, when the current from the monitoring photodiode exceeds the adjustable range of the laser driver, the laser driver cannot regulate the laser output power. As a result, a mechanism that can extend the adjustable range of laser drivers to regulate the target output power of a laser in the TOSA of an optical or optoelectronic module when the current from a monitoring photodiode a relatively high is desired.
This “Discussion of the Background” section is provided for background information only. The statements in this “Discussion of the Background” are not an admission that the subject matter disclosed in this “Discussion of the Background” section constitutes prior art to the present disclosure, and no part of this “Discussion of the Background” section may be used as an admission that any part of this application, including this “Discussion of the Background” section, constitutes prior art to the present disclosure.